Fix hg clone race with writer
Most read operations in hg don't need locks because we order reads and
writes for consistency. Clone is an exception to this as we're copying
entire file histories and could end up with more file history copied
than we have commits.
For now, make clone take a lock on the source repo. Non-hardlinked
clone should eventually be changed to use lockless pull.
+ hg init
+ hg add foo bar
+ hg commit -m commit text -d 0 0
+ hg clone A1 B1
+ hg remove bar
+ hg commit -m commit test -d 0 0
+ hg commit -m commit test -d 0 0
+ hg clone A1 A2
+ hg clone B1 B2
+ hg pull ../B1
pulling from ../B1
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
+ hg update -m
+ hg commit -m commit test -d 0 0
bar should remain deleted.
+ hg manifest
6b70e9e451a5a33faad7bbebe627e46b937b7364 644 foo
+ hg pull ../A2
pulling from ../A2
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files
(run 'hg update' to get a working copy)
+ hg update -m
+ hg commit -m commit test -d 0 0
bar should remain deleted.
+ hg manifest
6b70e9e451a5a33faad7bbebe627e46b937b7364 644 foo